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Impulse generator
Buš, Ondřej ; Drexler, Petr (referee) ; Kubásek, Radek (advisor)
This thesis deals with the question of generating very short voltage impulses. At first it considers the most used behaviors of impulses and their mathematical description. Then it covers various principial circuit connections, which are used for generating short impulses. There is a scheme of controlled generator described in detail in this work, which is being used for exciting the forming circuit. Part of this work is also a description of program equipment, scheme of connection with designed desk of printed circuit. Description of construction of three shape circuits based on theoretical findings follows. Every solution is compared to each other upon time and frequency domain.
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Relaxation times in the polymer gel electrolytes by magnetic resonance methods
Jehličková, Lenka ; Kadlec, Radim (referee) ; Kubásek, Radek (advisor)
The purpose of this Bachelor’s thesis is measuring of gelly structure relaxation using magnetic resonance imaging. The first part closely describes the theory needed for upcoming measuring. There is explained basic physical principle of NMR and terms such as precession, Larmor frequency and RF pulses are established. The measuring instrument is also schematically introduced, as are its main parts and division in aspect of magnetic fields. The most important part is explanation and understanding of relaxation processes that happen during NMR. Individual sequences used for measuring of relaxation processes are demonstrated by the spin echo method, which is the basic building block of all successive methods. The second part is processing of results. Measuring of fall and spectre of given gelly samples is expressed as a function of time T2 on the sample solidification time.
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Estimation of instantanenous frequency
Mik, Šimon ; Mikulka, Jan (referee) ; Kubásek, Radek (advisor)
This bachelor’s thesis describes different instantaneous frequency estimators. Various methods are implement into Matlab software and there are introduced conclusions of testing. Methods are compared in two aspects. The first aspect is accuracy of method which depend on time progress input signal. The second aspect is accuracy of method which depend on ratio frequency of input signal and sampling frequency. Outcomes of tests are compared. The result of this work is evaluate properties each method.
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Time-frequency analysis
Tráge, David ; Hadinec, Michal (referee) ; Kubásek, Radek (advisor)
The aim of this bachelor`s thesis is to explore possibilities of solving time-, frequency analysis a their combination time-frequency analysis by different methods for example Fourier transform a Wavelet transform. Going through this project we will get know each transformation and we will make clear procedure of their solving and first of all their advantages and disadvantages in view of accuracy of frequention`s mark in time.
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Methods of weighting the magnetic resonance signal
Filla, David ; Kubásek, Radek (referee) ; Hadinec, Michal (advisor)
The objective of this project is introduction to the fundamental principle of magnetic resonance and to the basic measuring methods used in MR. There is also described how to set parameters of pulse sequences in different measuring methods to obtain an image weighted by relaxation T1, relaxation T2, diffusion and eventually proton density. In the experimental part, we have measured images of three samples (tomato, pepper and mandarin) by four methods (SE, GE, IRSE and IRFSE). For obtained measured images we have proceed phase correction, created T2 and T2* maps. Then we consider the images obtained in terms of quality and compare with each other.
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Spectral impuls signal analyzis
Měcháček, Radek ; Kubásek, Radek (referee) ; Fiala, Pavel (advisor)
Analysis signals, especially then pulsed signals and their next processing, today alreadyquaere to many different technological line. From communication engineering over telecommunication and acoustics, after as much as field - club application or multimedia. This work is introduction to the problems methods processing pulsed signals. Is distributive how from the standpoint of theory, so from look future application usage, by the help of programmatic analyses basic signals. Work bears basic description, notions, routes and method for work and analysis with widthspectral and ultraswidthspectral signals. Further be created tool for generation, filtration and near processing of several basic pseudo - random signals.
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Measurement of gradient magnetic field decay in MR tomograph
Kubásek, Ondřej ; Kubásek, Radek (referee) ; Bartušek, Karel (advisor)
The objective of my thesis is to measure magnetic field gradient decay in an MR tomograph, process and evaluate the data measured and analyse the issue. The theoretical section focuses on the reasons for the gradient distortion which has a negative impact on NMR measuring techniques and it also describes options to eliminate the negative effects, focusing mainly on pre-emphasis filtration. It also lists methods of gradient magnetic field measuring. The practical section contains results of magnetic field decay measurements taken with the tomograph in the Institute of scientific instruments of the Academy of sciences in Brno using the method of instantaneous frequency with and without pre-emphasis compensation. The data are processed with MAREVISI and MATLAB programmes. MATLAB is used to develop a modern method of filtration to eliminate noise in useful signal leading to more accurate measurements of MR magnetic fields. This filtration uses a method of time-dependent variable thresholds and two-channel filter banks. MATLAB is also used to design a programme for approximation of the measured gradient magnetic field decay. The decay must be approximated in order to obtain time constants and the degree of exponential decay, which serve to set up the pre-emphasis compensation.
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Noise generator
Pospíšil, Miroslav ; Kubásek, Radek (referee) ; Fiala, Pavel (advisor)
The goal of bachelor’s thesis „Noise generator“ is circuit design and construction of noise generator. The first part is concentrated on description of random signals. There are circuits of noise generators in the second part. In the third part is example of utilization noise generator in microwave sensors. And in fourth part are designed circuit and made measurements.
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Image signal processing by wavelet
Slávik, Vladimír ; Gescheidtová, Eva (referee) ; Kubásek, Radek (advisor)
The first part of text introduces reader to basic theory of wavelet transform and its realization by filter banks. WT of two-dimensional signals is shown and a particular application of WT in this domain - signal denoising, is discussed. The second part describes the application for image denoising realized in MATLAB from both user's and programmer's viewpoint.
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